Vehicle fuel systems comprise, among others, a fuel tank fitted with a filler neck, a variety of fuel valves, a tubing for supplying fuel to the ignition system and a fuel vapor treating system (typically a carbon recovery system--canister) to which fuel vapor from the fuel tank flows and is then used for enriching the fuel mixture fed to the ignition system.
Fuel fluid from the fuel tank flows via the one or more valves which are connected, via suitable tubing, to an expansion tank intermediate the fuel vapor recovery system and the tank.
The expansion tank receives fuel fluid flowing from the fuel tank which flow at a relatively high velocity owing to pressure and temperature changes, and thus vapor flowing from the fuel tank carries along with it also a considerable amount of fuel liquid in the form of droplets (as a result of venturi effect). The expansion vessel traps the fuel liquid and allows fuel vapor flow towards the vapor recovery system. The fuel liquid then returns back to the fuel tank via the tubing.
Expansion tanks are typically fitted with a roll over valve (ROV) whereby in case the vehicle rolls over, fuel liquid trapped in the expansion tank does not escape and cause hazardous risk. Alternatively there is fitted a fuel level limit valve (FLVV).
Prior art expansion tanks are made of a housing formed in a blow-molding process, as a single unit, with at least two nipples fitted thereto for connecting the respective tubing thereto. The attachment of the nipples to the housing and the attachment of the respective valve within the housing are carried out by welding, whereby the respective welding areas are not impermeable to fuel vapor, as now required in accordance with many safety and environmental standards. Other expansion tanks are made of metal and are thus expensive as they require more labor in manufacture thereof, in particular as welding is required.
It is an object of the present invention to provide an expansion tank for a vehicle's fuel system, which expansion tank is made of a plastic material and which nevertheless is essentially entirely impermeable to fuel vapor.